A) Field of the Invention
This invention relates to a driving method of a solid-state imaging apparatus.
B) Description of the Related Art
Recently in imaging according to a solid-state imaging apparatus, a kind of line culling that reads a signal line at a fixed interval is executed. For example, as disclosed in Japanese Laid-Open Patent Hei11-261901, it is well known that the solid-state imaging apparatus reads signal electric charges from photoelectric conversion elements to a vertical signal charge transfer device by culling one third of the signal lines in the vertical direction and outputs the read signal electric charges after adding every two lines of them in a horizontal electric charge transfer device.
FIG. 11 is a timing chart showing a driving timing of the conventional solid-state imaging apparatus. FIG. 12 is a diagram for explaining signal charge transfer by the driving timing shown in FIG. 11. On a lower side of the drawing, an enlarged timing chart of timing t1 to timing t5 in the driving timing shown in FIG. 11 is presented, In the drawing, a black part represents an electric potential barrier, a white circle represents an empty signal, a hatched circle represents a signal charge (for example, a red color signal), and a crosshatched circle represents another signal charge (for example, a blue color signal).
At the timing t1, signal charges are read from the photoelectric conversion elements to the vertical electric charge transfer device by impressing high level (VH) pulse on electrodes V3B and V3A so that the two thirds of the signal lines in the vertical direction are read out. Then, the read signal charges are transferred for two steps to the down stream by the timing t2 by alternatively impressing mid level (VM) and low level (VL) pulses to the electrodes V1B to V4A.
Moreover, a dummy signal and an OB signal are sequentially transferred to an output circuit by the horizontal electric charge transfer device during this period.
Between the timing t2 and timing t3, the signal electric charges are transferred for one step, and one of two read signal lines (on the down stream) is transferred to the horizontal electric charge transfer device. Between the timings t3 and t4, the signal electric charges are transferred for one more step, and the empty signals are transferred to the horizontal electric charge transfer device. Between the timings t4 to t5, the signal charges are transferred for one more step, and another one of two signal lines (on the up stream) is transferred to the horizontal electric charge transfer device, and the signal electric charges on the down stream and the up stream are added in the horizontal electric charge transfer device.
For example, in a case that the electric potential in the vertical electric charge transfer device is not uniformed, and when the signal electric charges are transferred from the vertical electric charge transfer device to the horizontal electric charge transfer device, vertical transfer effectiveness will be lower, and left-behind electric charges may be generated. In this case, the left-behind electric charges on the down stream transferred to the horizontal electric charge transfer device at the timing t2 in FIG. 11 and FIG. 12 are transferred to the horizontal electric charge transfer device with empty signals transferred to the horizontal electric charge transfer device at the timing t3; however, another left-behind electric charges on the up stream are transferred to the horizontal electric charge transfer device with the signal charge transferred to the horizontal electric charge transfer device later and corresponding to the different color. By this color blending, image defection such as longitudinal line and the like on the image signal to be output is generated, and the image may be confused.